A DC-DC converter mounting thereon a coil component has been used in an electric power source of a mobile communication terminal, etc. A laminated type coil component (multilayer coil component) is used as the above coil component from the standpoints of downsizing, etc. Such a multilayer coil component is disclosed in, for example, Japanese Unexamined Patent Publication No. 2010-192715.
In this regard, when a via hole conductor connecting coil conductors adjacent to each other in a laminated direction is arranged inside a coil formation area in plan view like the multilayer coil component disclosed in Japanese Unexamined Patent Publication No. 2010-192715, an end of the coil conductor connected to the via hole conductor enters inside the coil, substantively reducing the coil inner diameter. Such a reduced coil inner diameter makes it difficult to yield sufficient coil characteristics (for example, inductance and Q-value).
Japanese Unexamined Patent Publication No. 2015-18852 has proposed a technique that prevents reduction of coil inner diameter by disposing a conductive pattern having functions same as those of the via hole conductor in the coil formation area in plan view.